1. Field of the Disclosure
The disclosures relates to a method for manufacturing composite systems made of metal and polymer shaped parts, especially of metal/rubber composite systems.
2. Related Technology
Methods for manufacturing metal/rubber composite systems have been known for some time and are becoming increasingly important, e.g. in automobile construction. Such composite systems are distinguished by the fact that they combine the advantageous properties of metal and rubber, i.e., on the one hand, they are rigid and torsion-resistant and on the other hand they also have permanent-elastic properties. In addition, such composite systems regularly have a lower intrinsic weight compared with alternative devices.
Hitherto, substantially two methods for manufacturing metal/rubber composite systems have been available to the person skilled in the art for stabilizers, bushings, axle bearings, especially in the chassis area, stops, buffers, especially for supporting arms for aggregate bearings, or sleeve bearings, especially torsion-bar shoulder bearings and/or the like. According to a first method, metal parts inserted in a vulcanizing tool are first surrounded with an unvulcanized elastomer, e.g., sprayed around, whereupon the vulcanizing yields a metal/rubber composite. In order that useful bond is found between rubber and metal, an adhesion system is usually required which is to be applied to the metal parts to be used in a first step. Such a method is described, for example, in EP 0 684 404 A1. This method, also known as vulcanisation, usually requires long cycle times since the metal part must initially be heated to a pre-determined temperature. Since the metal part must be inserted in the vulcanizing tool, a special vulcanizing tool usually needs to be made for each newly shaped composite component. In addition, only a comparatively small number of tool calibres can be realized. It is also disadvantageous that in order to be able to insert the metal parts reliably and reproducibly in the vulcanizing tool, a considerable expenditure on apparatus is required. Furthermore, the demolding process of the finished composite components does not always proceed problem-free, especially since the vulcanisation takes place at high pressures so that a considerable proportion of waste must usually be accepted. Finally, the surface of the metal parts in the vulcanizing tool is frequently damaged, e.g., in the form of pressing edges. In order to nevertheless achieve usable metal/rubber composite systems, great care must be taken both when inserting the metal part into the vulcanizing tool and during the demolding process. As a result, very long processing times on the vulcanizing press are additionally obtained. Thus, not only the vulcanizing duration but also the tool handling as such contribute to long cycle times. In addition, an increased liability to corrosion is observed for metal parts provided with unvulcanized elastomer sleeves. The vulcanizing method is particularly expensive, for example, if a sleeve bearing is to be manufactured. Sleeve bearings are usually composed of a rigid outer sleeve and a rigid inner sleeve mounted coaxially therein at a distance, which are bonded by a sleeve of elastomer material.
In a second so-called postbonding method, an already partially vulcanized rubber shaped part is used. The rubber shaped part is fixed and pressed on a metal part using a clamping device while generating the highest possible pre-stress before a bond is produced between metal and rubber in an annealing furnace while completely vulcanizing the rubber shaped part. In this method also, the metal part is usually provided with an adhesive layer. Such a postbonding method is described for example in DE 199 19 573 A1 for the manufacture of a torsion bar shoulder bearing. A reliably adhering bond is however only obtained if the heating period at a pre-defined temperature is not too short and is in the range of at least 20 to 40 min. In practice, however, the tempering times are frequently even 60 to 90 min. This necessarily results in relatively long cycle times. In order to be able to work profitably with the method according to DE 199 19 573 A1, high numbers of pre-assembled metal/rubber systems which are each to be fixed and pressed with a plurality of separate clamping devices, regularly need to be inserted in the furnace. In addition to a high expenditure on equipment, a high work expenditure which is incurred, for example, by the assembly and dismantling of the clamping devices, generally cannot be avoided. It is also disadvantageous in the method according to DE 199 19 573 A1 that only suitable are those elastomer shaped parts which when demolded, are cross-linked free from bubbles on the one hand and on the other hand, are not yet completely vulcanised so that free vulcanisation valences are still present in the elastomer. On the whole, therefore, the postbonding method is very expensive and cost-intensive, especially for manufacturing larger numbers of items.
In the field of manufacturing cables or metal wires coated with rubber, further methods unsuitable for the manufacture of shaped parts are known. Thus, for example, according to U.S. Pat. No. 3,695,228 unvulcanized rubber is used in tire manufacture, especially in the manufacture of tire cores, where a metal wire provided with unvulcanized rubber is guided through a metal coil attached in a pressure chamber, which generates a high-frequency induction field. In this way, a rubber coating is obtained with a high degree of vulcanisation in the vicinity of the metal wire and a low degree of vulcanisation in the outer edge region of the rubber coating. This outer region is accordingly sticky and easily adheres to any surfaces so that the coated wires cannot easily be handled separately and generally are not handled separately. In addition, the use of a pressure chamber to produce this coated wire necessarily limits the geometry and size of the coating bodies which can be used. The method according to U.S. Pat. No. 3,695,228 is thus not suited for the mass production of individual parts. Technical rubber shaped parts are not accessible in this way.
Induction heating is also used, for example, to activate at adhesive material. WO 96/21550 discloses the activation of an adhesive between a metal part and a rubber part surrounding this by means of an induction field.
Furthermore, the activation of an adhesive via an induction field during the manufacture of bonded plastic and metal profiles is also known from DE 31 08 221 A. Moreover, induction fields are also used to bond surfaces of thermoplastic plastics with one another or with other materials such as paper or cardboard. Thus, CH 463088 A discloses a method in which a metal foil, especially an aluminium foil, is inserted between two surfaces to be bonded, for example, between two plastic surfaces and is then inductively heated so that a thermoplastic plastic foil or thermoplastic plastic lamination is formed. Such foils or laminates are especially suitable for water-vapour and aroma-proof packaging but not for the manufacture of shaped parts, especially sleeve bearings.
According to DE 30 38 069 A1, an induction field can also be used in the manufacture of disposable cannulas of disposable syringes by melting a metal cannula tube in a plastic attachment by temporally producing heating current heating in the region of the cannula tube adjacent to the attachment to melt the plastic of the attachment on the cannula tube.
In addition, according to JP-04267131A a glass-fiber-reinforced nylon gearing is fixedly attached to a steel shaft by applying a high-frequency induction field in which fusion takes place in the contact region of the gearing with the shaft.